Tank filler devices and systems are known which can transfer vaporizable liquids from a fuel storage facility to a tank and, in addition, return the vapor escaping from the tank being filled to the supply tank or other storage means from which the fuel supply is being delivered. Such systems have been proposed for use where it is desired to prevent the escape of fuel vapors to the atmosphere during tank filling operations. Some such systems have utilized coaxial conduits having sealing means connecting with the outer edge of the tank filler opening so as to retain vapor escaping therefrom and carry it into the supply facility through an outer passage while delivering liquid fuel into the filler opening through a coaxial inner passage-defining nozzle.
Diesel locomotives generally are provided with fuel tank filler systems involving a quick connecting coupling and a large diameter filler pipe, for example 21/2 inch, through which diesel fuel is delivered to the locomotive fuel tank at rates of several hundred gallons per minute. Closed vent vapor return systems have not generally been used, since the volatility of diesel fuel is relatively low and the fuel, if spilled, is relatively difficult to ignite. However, consideration is being given to the possible use of alternative more volatile fuels, such as methanol, for combustion engines in locomotives as well as in other applications for which it may be desirable to provide a closed vent vapor return filler and to minimize the spillage of fuel and escape of vapors from the system during filling. Coaxial filler and vapor recovery systems are available for commercial delivery of gasoline to automotive service stations and the like and might be adopted for locomotive tank fillers. However they are relatively heavy and could be awkward to attach to a filler pipe located on the side of a locomotive. In addition, their cost is relatively high.